OK - I was able to back back as far as the 1600's with the stato records! Amazing since the stato begins in 1809 but thanks to the longevity of Raffaele Napolitano who lived to be 98, his father Paolo would have been born in the 1600's. That is great but I started out wanting to find my grandfather's half brother's family and half sister's families. I still have nothing on them other than their names and birthdates. Here is all I know:
Enrico DeSeta born in 1901 and immigrated to Argentina
Delfina DeSeta Born: 1898 - probably lived and died on my grandfather's farm. I know he left the farm to one of his sisters so the eldest is the most likely.
Emilia Born: 1899 Moved to Paola and married Peppino Sinforoso there. The comune di Paola can find no children for them.
Antoinetta Genovaffa Born: 1903
Carmela Born: 1903
Alfredo Born: 1906 died 1907

Does anyone know what I can do to find out who and when his sisters married so I can attempt to find their children?

You can request to Anagrafe and Stato Civile of Montalto Uffugo, if there is any family record about Delfina, Emilia, Antonietta Genoveffa and Carmela.
If all these people lived longer, for sure there is something at Anagrafe.
Anagrafe records state everything about a person like: where resident (address), if moved to another address or emigrated abroad, when married, when died.
I hope I was clear.
I suggest you to send me a specific and detailed letter stating all the dates, names and everything, so you can request copy of anagrafe records in order to know if there is any descendents of them
Also you can request "Stato delle anime" parish census, so you can understand more where this people use to live
bye Riccardo

Great Riccardo! Of course my first question is are these records free? I have heard tales of people spending hundreds of dollars and I just don't have that kind of money right now. Where would I send a request for the "Stato delle anime"? The church or the comune? I will write something and email it to you so you can let me know if I have provided enough information. Thanks Riccardo!

Well, the certificates from anagrafe are free, maybe you need to pay some change or expenses for shipping.
What costs a lot is a family certificate (not all the muncipalities let it pay).
This certificates costs € 15 euros plus € 3/€ 6 euros per name found.
The request for Stato delle anime should be sent to the parish they belonged to.
I hope it helps
bye Riccardo

Cathy,
write this way in order to request if there is any infos of Giuseppe Napolitano siblings and their descendents (if any)
Also add copy of your ID + big self addressed envelope + 3 International reply coupons.
When it is done before you sent it, send it to me. It has to be perfect, so maybe in a couple of weeks I can call Montalto Uffugo to see what is going on and to speed up the process
I hope it helps
bye Riccardo

p.s. when u write a date of birth for the people below first write the number of the day, then the month (in words, not in number) and then the year
-------------------------

Comune
Ufficio di Stato Civile
Via Municipio
87046 Montalto Uffugo (CS)
Italy

Oggetto: Ricerca fratelli DeSeta e loro discendenti

Egregio sig. Sindaco,
mi chiamo Cathy Napolitano e scrivo dall'Illinois, USA
Con la presente le scrivo per potere conoscere tutti i dati anagrafici dei fratelli di mio nonno e dei suoi discendenti.
Mio nonno si chiamava Giuseppe Napolitano nato a (place of birth) il (date of birth - day-month-year) figlio di (name of his father and his mother)
Le persone di cui sotto erano figli di (name and last name of father and mother of the people stated below):

1) Enrico DeSeta nato a Montalto Uffugo il day month 1901 ed emigrato in Argentina
2) Delfina DeSeta nata a Montalto Uffugo il day month 1898
3) Emilia DeSeta nata a Montalto Uffugo il day month 1899.
Emilia si è trasferita nel comune di Paola, dove ha sposato Peppino Sinforoso il (date of marriage - day-month-year). Il comune di Paola non ha trovato alcun discendente.
4) Antoinetta Genovaffa DeSeta nata il day month 1903
5) Carmela DeSeta nata il day month 1903

Se dalla vostra ricerca dovesse sortire un esito negativo, le chiedo cortesemente di potere ricevere una risposta negativa su carta intestata del vostro ufficio.

Allego alla presente: copia del mio documento di identità, busta per la risposta e n.3 buoni di risposta (IRC) facilmente scambiabili in francobolli presso qualunque ufficio postale.

La prego di inviare il tutto all'indirizzo di cui sotto.
Rimango in attesa di cordiale riscontro, le auguro buon lavoro e porgo distinti saluti

your complete name

your signature

your address
your town
zip code
country
-----------

Thank you Riccardo!!!
Should I enclose copies of their birth acts? Would that be helpful?

Cathy, just add the date of birth, enclosing birth acts don't help
let me know
bye Riccardo